Add missing dsl pool configuration lock

The semantics introduced by the restructured sync task of illumos
3464 require this lock when calling dmu_snapshot_list_next().
The pool is locked/unlocked for each iteration to reduce the
chance of long-running locks.

This was accidentally missed when doing the original port because
ZoL's control directory code is Linux-specific and is in a
different file than in illumos.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1785
Dedup-related documentation additions for zpool and zdb.

Document the "-D" and "-T" options and the optional interval
and count or "zpool status".

Also for zpool's man page, use a consistent order for the
various "-T" options to match the program's help output.

Document the effect of additional "-D" options for zdb.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1786
Linux 3.11 compat: Rename LZ4 symbols

Linus Torvalds merged LZ4 into Linux 3.11. This causes a conflict
whenever CONFIG_LZ4_DECOMPRESS=y or CONFIG_LZ4_COMPRESS=y are set in the
kernel's .config. We rename the symbols to avoid the conflict.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1789
Increase default udev wait time

When creating a new pool, or adding/replacing a disk in an existing
pool, partition tables will be automatically created on the devices.
Under normal circumstances it will take less than a second for udev
to create the expected device files under /dev/.  However, it has
been observed that if the system is doing heavy IO concurrently udev
may take far longer.  If you also throw in some cheap dodgy hardware
it may take even longer.

To prevent zpool commands from failing due to this the default wait
time for udev is being increased to 30 seconds.  This will have no
impact on normal usage, the increase timeout should only be noticed
if your udev rules are incorrectly configured.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1646